James 1:6

But let him ask in faith, nothing doubting: for he that doubteth is like the surge of the sea driven by the wind and tossed.

Again, James gives the teaching of Christ, who said, "Whatsoever ye pray and ask for, believe that ye receive them, and ye shall have them" (Mark 11:24).

Therefore, it is not merely faith in God which James had in view here, but faith in the Lord Jesus Christ. He was writing to Christians who, like himself, were servants of God and of Jesus Christ; and he had already mentioned their common faith a moment earlier in James 1:3. Modern exegetes who limit faith in the book of James to the mere belief in God are absolutely wrong. As Lenski said, "The older commentators who understood `in faith' to mean faith in Jesus Christ' are correct."[18]

He that doubteth is like the surge of the sea ... Not only does the doubter forfeit all legitimate expectation that his prayers may be answered, but something else appears in this verse, namely, that that one who is a wavering Christian, or unfaithful in the area of his highest responsibility, will also prove to be unstable and undependable in all other areas likewise. Many a man's forsaking the church has been the forerunner of his deserting his family, embezzling company funds, or plunging into a life of licentiousness.